Comparison of the Efficiency of Williamson and Anderson Turn Manoeuvre

Transcription

1 the International Journal on Marine Navigation and Safety of Sea Transportation Volume 9 Number 4 December 2015 DOI: / Comparison of the Efficiency of Williamson and Anderson Turn Manoeuvre K. Formela, M. Gil & H. Śniegocki Gdynia Maritime University, Gdynia, Poland ABSTRACT: The paper presents comparison of the Person over board manoeuvres. The article was based on research con ducted on a group of students of the Faculty of Navigation of Gdynia Maritime University. People involved in studies previously conducted on board training on school training ships: ʺDar Młodzieżyʺ and ʺHoryzont IIʺ, but did not have experience as an officers. Research was carried on the Polaris Ships Bridge Simulator, located at the faculty of Navigation, of Gdynia Maritime University. 1 INTRODUCTION Safety of navigation is one of the key issues affecting the transport processes, which are used for maritime transport. Among the many threats that could undermine the proper course of the voyage, accidents related to the man falling overboard belong to a small group of events that can take place regardless of the hydro meteorological conditions, specifics of the operated water area, traffic intensity, or other external circumstances. Despite the tendency to constantly improve the level of safety for oversea vessels, correct response of the ship navigator, resulting in the correct implementation of the required ʺman overboardʺ manoeuvre is not always observed. The issue of POB (Person Overboard) accidents is therefore still valid, particularly that for a decade you can see steady growth of the world merchant fleet, which over the last eight years has increased by vessels [European Maritime Safety Agency ]. Figure 1. The number of the world merchant fleet in years [European Maritime Safety Agency ]. 2 SIMULATION STUDIES Because of the direct impact of the ʺman overboardʺ manoeuvre on to the rescue of human life at sea, the members of the Scientific Society ʺWatchersʺ active at the Faculty of Navigation of Gdynia Maritime 565

2 University, decided to carry out the relevant research in order to determine the effectiveness of individual manoeuvres. The measurement part consisted, successively, of the ʺWilliamson Turnʺ and the ʺAnderson Turnʺ performed by two groups of 17 students of the Navigation Maritime Transport Faculty. Persons involved in the studies previously underwent the seagoing service onboard of training vessels s/v ʺDar Młodzieżyʺ or ʺHoryzont IIʺ. Selected for testing was navigation and manoeuvring simulator, POLARIS type, manufactured by the Norwegian company named Kongsberg. All devices operate on the basis of complex mathematical models that provide realistic reactions of an individual and his environment. In addition, they have DNV (Det Norske Veritas) certificate confirming the possibility of their use during specialized courses for crews of merchant ships). In the designed task a man was initially held at a distance of 380 m from the bow of the vessel so that the vessel, when floating past the manʹs position, was positioned parallel to it. The applied solution made it possible to simulate a situation in which the victim has just fallen overboard. Information about the initiation of the POB alarm was sent to steering units with radio communications at a time when the survivor has passed the right traverse of the ship. In practice, this meant the circumstances in which the distance from the initial position of the vessel to the POB position was about 500 m. Simulations were constructed in such a way so that the man placed in the water was not affected by the drift of wind, making his position constant during the entire manoeuvre. Since none of the tested persons had previous experience with the applied model of the ship, the first attempt was carried out in accordance with the description of the manoeuvre contained in the ʺInternational aviation and maritime search and rescue guideʺ (IAMSAR). Figure 2. Simulators used for researches [Gil, Śniegocki 2015]. 2.1 Objectives and course of the studies According to the assumptions, each of the tested individuals performed the exercise three times manoeuvring to the starboard. All participants were operating in the same water area and with the same hydro meteorological conditions, which are shown in Table 1. Table 1. Hydro atmospheric conditions simulated in the researched water area [Gil, Śniegocki, 2015]. Depth 100 m on the entire working area Wind speed and direction Sea State Current speed and direction kn (2 B) 1 Calm (rippled), 0 0,5 m none Air temperature 21 C Visibility 8 very good 10 Mm Clouds No clouds, clear visible sky To accomplish the task the BULKC06L model was selected it is a fully loaded, 215 meter bulk carrier with a displacement of more than tonnes [Kongsberg Maritime, 2015]. In order to shorten the exercise, it was beginning with a course 000 with the settings of an engine order telegraph (E.O.T.) ʺFULL SPEED AHEADʺ and the maximum speed of the ship 15.9 knots. Figure 3. Anderson Turn (a) and Williamson Turn (b) as per IAMSAR [International Maritime Organization, 2008]. If as shown in Figure 3, the guide containing the guidelines of the International Maritime Organisation (IMO) suggests the following sequence of action in case of an immediate manoeuvre the ʺAnderson Turnʺ [International Maritime Organization, 2008]: Move the rudder on the side from which a man fell; After reaching a change in the course by the value of 250, set the rudder in the ʺzeroʺ position; In the case of the ʺTurn Williamsonʺ manoeuvre IAMSAR recommends the following procedure [International Maritime Organization, 2008]: Move the rudder on the side from which a man fell; After reaching a change in the course by the value of 60, set the rudder on the opposite side; When the course reaches the value lower by 20 than the counter course as compared to the initial settings of the vessel, set the rudder in the ʺzeroʺ position. Both at the first and the second manoeuvre, the initiation and intensity of the process of stopping of the vessel was carried out at the discretion of an individual performing the exercise. During the 566

3 research further tests were carried out on the basis of previous experiences of participants. At the time of the exercises execution, those involved in the exercise modified the course of the manoeuvre in accordance with their convictions based on the analysis of the chart showing the route of the first test. Each approach was considered as completed when the navigated vessel had reached a speed of less than two knots. That criterion was adopted due to the recognition that such speed level was sufficient for safe deployment of a rescue boat. During the exercise, at the position of an instructor (a technical operator of the simulator) they recorded the following real time dynamic parameters of the vessel, in two second intervals: reference number of a measurement; duration of the exercise [hh: mm: ss]; course [ ]; direction of the water route [ ]; speed [knots]; speed change [knots / min]; latitude; longitude; heading (HDG) [ ]; actual position of the rudder [ ]; defined position of the rudder blade [ ]; rate of turn [ / min]. rectangular coordinates and their counterparts on the ellipsoid of revolution (spheroid). In order to increase the accuracy of the obtained calculations they used the Gauss Krüger coordinate system reproduction for the axial meridian 006, based on the following relationships [Specht et al. 2013]: L 2 S B xkr sin Bcos B R L B B t L sin cos sin( B) cos B 6158t t t L y Lcos( B) cos B 1t L cos B5 18t t t After obtaining the rectangular coordinates they calculated the average position of all measurements and the distance separating the ship from the position of man at the end of the manoeuvre. For this purpose they applied the properties of a loxodromic triangle and similar calculations were performed for the data obtained. Figure 4. Recorded tracks and data. Preview on the instructor station. 3 DEVELOPMENT OF THE COLLECTED DATA After collecting all the measurements, it was necessary to extract from them those parameters that ultimately were to be used to investigate the effectiveness of POB manoeuvres. The described attributes included: execution time of the ʺWilliamson Turnʺ and the ʺAnderson Turnʺ along with the stopping of the vessel (tm), as well as latitude and longitude (φ, λ) at the end of the manoeuvre (VK <2 knots). 3.1 Coordinates transformation For the implementation of the charts being the projection of obtained final positions of the ship on the plane, it was necessary to transform the geographical coordinates to Cartesian X, Y. For this purpose they applied the relationship between Figure 5. Spread of received final positions with respect to the POB position for the Williamson Turn and the Anderson Turn. 3.2 Breakdown of the results with respect to implemented trials Following the alignment of geographical coordinates they analysed the results as divided into three attempts. They sorted and counted the average values of the distance (from the POB position) and the duration for individual approaches. The summary of results is presented in Table

4 Table 2. Average values of manoeuvres time and distances to a man for individual tests. Williamson Turn Anderson Turn Attempt DPOB [m] tm [min] DPOB [m] tm [min] According to the above a table can be seen a gradual shortening of the duration of manoeuvre of each successive trial especially in the case of the ʺWilliamson Turn.ʺ This fact results from a practical familiarization of a tested individual with the handling/manoeuvring characteristics of the vessel and the modification of the generalized scheme of action based on the analysis of the earlier manoeuvre. 4 CALCULATION OF EFFICIENCY OF POB MANEUVERS In order to test the effectiveness of the manoeuvre, it was necessary to allow the indicator to quickly determine whether a manoeuvre had been performed successfully. While attempting to define a model describing the indicator, the following requirements were accepted: zero dimensionality; obtained values 1; taking into account the time of a manoeuvre (tm); taking into account the distance of the ship from a POB position (DPOB); being shot manoeuvre ʺman overboardʺ; grasping the essence of the POB manoeuvre performance. Given the above assumptions, it was decided to translate all the values obtained to one form. Because tm is not the total time that separates the commencement of a ʺPOBʺ type manoeuvre by a ship until rescuing a man, it was necessary to determine the total duration of the manoeuvre (tc). For this reason all its components were summed: tc tm tl tr Figure 6. Graph with average duration of the manoeuvres in particular attempts Based on the results concerning the course of the ʺWilliamson Turnʺ it can be concluded that the smallest distances from the average position and the position of man were obtained at the second attempt. In the case of the ʺAnderson Turnʺ the approach results in both the 2nd and 3rd trial were very close, but definitely different from the results obtained in the 1st approach. This may result from the analyses of the previous manoeuvre carried out by students, getting practically acquainted with the properties of a marine vessel and the implementation of amendments to the generalized scheme of manoeuvre proposed in the IAMSAR. The values obtained at the third time (especially in the case of the ʺWilliamson Turnʺ) being smaller than at the first approach, while higher than at the second, may result from probably too much confidence emerging in the helmsman who noticed a significant improvement as compared to the manoeuvre implemented as the first one. This may result in a reduction of concentration, being at ease, and ultimately getting worse results. Visible differences between the results obtained with both manoeuvres are slightly different in the case of the ʺ270 turn data are similar. This is probably due to the simplicity of executing of the said manoeuvre and the limited ability to modify the approach itself. In the case of the ʺWilliamson Turn,ʺ which is assumed to be a longer manoeuvre, the differences in the results obtained in subsequent attempts are much more apparent. where tm = duration of POB manoeuvre [min], tl = duration of rescue boat launching [min], tr = time required to pass DPOB distance by the rescue boat [min]. t r DPOB V r where Vr = rescue boat speed [kn]. Due to the assumption regarding the occurrence of the worst conditions in accordance with the charts presented in the IAMSAR they assumed the average smallest amount of time a man can survive in the water with the lowest test temperature, namely 60 minutes. Figure 7. Effects of the hypothermia in different water temperatures [11]. 568

5 According to the accepted model the G indicator was calculated for all measurements made. The most effective manoeuvre made by the student using the ʺAnderson Turnʺ reached a value of 0.263; while the least efficient For the ʺWilliamson Turnʺ the best value obtained was 0.380; and the worst Figure 8. G Factor for Williamson and Anderson Turn. Both from the above graph and the values obtained it follows that in the case of an immediate rescue action, when the moment of a man falling overboard was observed by a person leading the vessel or the crew on the bridge, the most effective method of approach to a man from among those described above is the ʺAnderson Turn.ʺ It is worth noting that even the most effective test performed while applying the ʺWilliamson Turnʺ was only slightly better than the least effective approach using the ʺsingle turnʺ method. As the obtained results show, the biggest impact on the effectiveness of the manoeuvre has the time of its execution, and in a lesser extent the distance between the ship and the man. An example of such measurement can manoeuvre in which with ʺTurn Williamsonʺ achieved DPOB = m (which is a value close to the average). G totalled 0.344; which is the second of the best values obtained. This was possible due to the favourable overall time manoeuvre tc = min. An example of such measurement can be a manoeuvre in which an application of the ʺWilliamson Turnʺ helped to achieve DPOB = m (which is a value close to the average). G totalled 0.344; which is the second of the best values obtained. This was possible due to the favourable overall time of the manoeuvre tc = min. 5 CONCLUSIONS Based on the carried out survey it was found that the greatest impact on the effectiveness of the implemented manoeuvre is that of the acquired experience. From the presented charts it follows that with each new attempt, the duration of the manoeuvre was reduced. The variable that most significantly affects the presented efficiency ratio of a manoeuvre is tm, so one can conclude that every next POB manoeuvre performed by the same person was more effective. The research shows that, especially in good hydro atmospheric conditions, the distance between a man and a stopped vessel is less important than the duration of the whole manoeuvre. This is because it is faster and more precise to reach the position of a man with a rescue boat rather than to approach him by a ship. It was not tested how the aforementioned situation affected the effectiveness of the manoeuvre in circumstances in which, due to the occurrence of adverse weather conditions, there is a need to shield the man and the rescue boat from the sea waves. The presented results also demonstrated the superiority of the ʺAnderson Turnʺ over the ʺWilliamson Turnʺ during the implementation of aforementioned manoeuvres in the immediate rescue operation. This is due to the simplicity of the ʺ270 turn,ʺ which translates directly into its duration and also efficiency. The values obtained indicate the saving of time of up to 5 minutes when the ʺAnderson Turnʺ is selected as a variant of the approach to the man who fell overboard, with respect to the mean values of all the times obtained by both methods. In a situation when the drowning man is overboard, this value is a huge gain for the benefit of all involved in the action. BIBLIOGRAPHY Gil M. & Śniegocki H., Efektywność manewru «Pętla Williamsona», Logistyka 4/2015, ss , European Maritime Safety Agency, The world merchant fleet in 2005 : Statistics from Equasis, European Maritime Safety Agency, International Maritime Organization i International Civil Aviation Organization, IAMSAR Manual : International Aeronautical and Maritime Search and Rescue Manual. London/Montreal: IMO/ICAO, International Maritime Organization, Resolution MSC.218(82): Adoption of amendments to the International Life Saving Appliance (LSA) Code. International Maritime Organization, International Maritime Organization, LIFE SAVING APPLIANCES: 2003 Edition, Combined edition. London: International Maritime Organiza tion, International Maritime Organization, Red., SOLAS: Consolidated Edition, London: International Maritime Organization, Kongsberg Maritime, Description of Ship Model : BULK06L: Version 14. Kongsberg Maritime, Specht C., Szot T., & Specht M., Badanie dokładności personalnych odbiorników GPS w pomiarach dynamicznych, Technika Transportu Szynowego, nr 10, ss ,